Some folks are pessimistic about the new lower-emissions 2007 engines; forecasts of rising costs and falling performance and reliability are common. Just don’t say that to the engineers and scientists who design, build, test and deliver the engines.

The EPA and California Air Resources Board restrictions don’t scare them. They challenge them. And it looks like the challenge is being met.

“I like the idea of clean air,” says Cummins Technical Advisor Glen T. Haegle. “Just give me a reasonable target and time to get there, and let’s go for it.”

Cummins ’07 engines are ready to go, and I test drove them through a variety of road conditions in Indiana to see if the mandatory changes designed to lower emissions would mean changes to the way you’ll drive ’07 tractors or how they’ll feel in your hands.

“It will be hard to tell the ’07 engines from the ’06 engines by appearance,” says New Product Marketing Manager Mario Sanchez. The only visible changes, obvious only if pointed out, are a crankcase breather housing and exhaust recirculation line on the driver’s side and, on the passenger side, a cooling tube and electric actuating motor for the variable geometry turbocharger. Beyond that the new and old engines look the same.

Nor will ’07 emissions compliance change a truck’s appearance. Exhaust systems will have Cummins Particulate Filters (CPF) similar in appearance and weight to the mufflers they replace.

Cummins’ 30 billion hours of testing has turned up no power or torque loss. “In fact, it’s expanding,” Sanchez says.

While appearance can be important, performance is what really matters in the end. So how do the ’07 engines compare to their predecessors? I went to the Cummins headquarters in Columbus, Ind., in March to test drive the ’07 ISX and ISM engines to find out.

The first test vehicle was a 2003 Volvo 770 condo with an ’07 ISX rated at 500 horsepower and 1,850 pounds-feet of torque, an Eaton 18-speed double-over and 3.73 rears. We hauled a 53-foot van. Including myself and technical advisor Pat Shook, who would accompany me for the ISX drive, the rig weighed about 77,000 pounds.

In this case, the CPF was vertically mounted behind the cab.

At the heart of Cummins’ exhaust gas recirculation and after treatment are its proprietary variable geometry turbocharger and CPF. The VG turbo controls the flow of gases through the engine: crucial to effective EGR. The CPF removes soot and ash from the exhaust.

In strenuous applications, the engines run hot enough to “passively” clean the CPF. For lighter work, a “dose” of misted diesel fuel injected upstream of the CPF “actively” creates the heat necessary for cleaning. The driver will not notice this. Even in the mildest, coolest-running applications, the system will use less fuel than a night of idling. Ash from burned oil additives collects in the CPF, and it takes about an hour once every two or three years to vacuum it out.

Cummins’ testing showed about the same or slightly better fuel efficiency as the pre-’07s, and improved reliability and durability.

My test began on U.S. 31, heading south from Columbus on Cummins’ 100-mile test drive route. The route includes city and rural driving, and two- and four-lane roads. It has flat land and genuinely challenging hills, particularly the narrow, 6-percent drop on state Hwy. 446, complete with hairpin curves, down to Lake Monroe (during which I was more concerned with safety than testing) the mile-long, equally steep climb back up, and the half-mile, 8 percent climb up “Kelly Hill,” just west of Nashville, Ind., on state highway 46.

It was sunny and clear. Pat and I chatted, but outside of town we soon encountered some 3- and 4-percent hills, a few of which were more than a half-mile long. I employed my standard torque/horsepower test formula: braked hard on the descents and started each climb in high gear at about 1,250 rpm and 50-55 mph: no running starts, just muscle. This is neither standard operating procedure nor the most effective way to drive a big truck, but it shows what an engine’s made of. The ISX chugged nonchalantly along, and I never had to drop a gear until we climbed up from the lake, where I dropped to 17th, and up Kelly Hill, where I dropped to 16th.

We got back, took a break, and then I climbed into the ISM test truck: an ’05 KW T600 with an ’07 ISM rated at 410 horsepower and 1,550 pounds-feet of torque, an Eaton 10-speed automatic and 3.90 rears. We hauled a 40-foot, drop-deck flatbed. Including myself and Technical Specialist Ryan Hedgecomb, my companion for the ISM drive, we weighed about 59,500 pounds. The CPF was horizontally mounted beneath the cab, just about directly below the passenger’s seat.

The ISM test drive was, if anything, smoother and even less eventful. The Eaton 10-speed shifted up and down as necessary. To more thoroughly test the engine’s power and torque, I locked in high gear and started the climbs at about 1,250 rpm and 50-55 miles an hour. The Eaton automatic would’ve dropped a gear had I let it. But like the ISX, the ISM pulled its load in high gear up all the hills except two without strain or complaint. As we climbed from the lake, the Eaton downshifted to ninth, and climbing Kelly Hill it dropped to eighth.

Upon returning to Cummins, I learned that the “dose” of misted diesel fuel does not “burn” the particulate matter collected on the filter. It creates heat sufficient for a chemical reaction that converts carbon soot and nitrous oxide to harmless carbon dioxide and nitrogen. The filter does not get hot enough to start a fire under the truck.

It sounds unusual, but the really big news was that I didn’t notice anything about the performances of the ISX and ISM that set them apart from other engines. They pulled just as hard and steady as, if not more than, their Cummins predecessors or any equally rated heavy-duty diesels. If the CPF actively cleaned itself with the “dose” of misted fuel, I never knew, nor would any driver.

Cummins is poised to produce the ISX and ISM engine and drivetrain combinations to customer specs, whatever they might be. Limited production begins this fall and will ramp up to full capacity next January.